JEE Main & Advanced Chemistry Organic Chemistry: Some Basic Principles & Techniques General Rules For Naming Organic Compounds

General Rules For Naming Organic Compounds

Category : JEE Main & Advanced

In the common system, all the isomeric alkanes (having same molecular formula) have the same parent name. The names of various isomers are distinguished by prefixes. The prefix indicates the type of branching in the molecule. For example,           

(1) Prefix n-(normal) is used for those alkanes in which all the carbon atoms form a continuous chain with no branching.                 \[\underset{n-\text{Butane}}{\mathop{C{{H}_{3}}C{{H}_{2}}C{{H}_{2}}C{{H}_{3}}}}\,\];   \[\underset{n-\text{Pentane}}{\mathop{C{{H}_{3}}C{{H}_{2}}C{{H}_{2}}C{{H}_{2}}C{{H}_{3}}}}\,\]           

(2) Prefix iso is used for those alkanes in which one methyl group is attached to the next-to-end carbon atom (second last) of the continuous chain.

           \[\underset{\text{Isobutane}}{\mathop{\underset{\,\,\,\,\,\,C{{H}_{3}}}{\mathop{\underset{\,|}{\mathop{C{{H}_{3}}-CHC{{H}_{3}}}}\,}}\,}}\,\] \[\underset{\text{Isopentane}}{\mathop{\underset{C{{H}_{3}}\,\,\,\,\,\,\,\,}{\mathop{\underset{|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,}{\mathop{C{{H}_{3}}-CH-C{{H}_{2}}C{{H}_{3}}}}\,}}\,}}\,\] \[\underset{\text{Isohexane}}{\mathop{\underset{\,\,\,\,\,C{{H}_{3}}\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,}{\mathop{\underset{|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,}{\mathop{C{{H}_{3}}-CHC{{H}_{2}}C{{H}_{2}}C{{H}_{3}}}}\,}}\,}}\,\]                

(3) Prefix neo is used for those alkanes which have two methyl groups attached to the second last carbon atom of the continuous chain.                                 \[\underset{\text{Neopentane}}{\mathop{\underset{\,\,\,\,\,C{{H}_{3}}}{\mathop{\overset{\,\,\,\,\,\,C{{H}_{3}}}{\mathop{\underset{|}{\overset{|}{\mathop{C{{H}_{3}}-C-C{{H}_{3}}}}}\,}}\,}}\,}}\,\]                \[\underset{\text{Neohexane}}{\mathop{\underset{\,\,\,\,\,C{{H}_{3}}\,\,\,\,\,\,\,\,\,\,\,\,\,}{\mathop{\overset{\,C{{H}_{3}}\,\,\,\,\,\,\,\,}{\mathop{\underset{\,\,\,\,\,|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,}{\overset{|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,}{\mathop{C{{H}_{3}}-C-C{{H}_{2}}-C{{H}_{3}}}}}\,}}\,}}\,}}\,\]

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